Introduction

On Good Friday, March 27, 1964, a 9.2 magnitude earthquake affected the south-central Alaskan region. This was the most powerful earthquake ever recorded in North America, and it lasted more than three minutes (Hansen,1966, pg 3), five times longer than an average size earthquake. Known as the 1964 Alaskan Earthquake, or the Great Alaskan Earthquake, it was a megathrust earthquake that caused over 131 deaths, thousands of aftershocks, huge tsunamis, and million dollars’ worth of damages.

Significant damages covered over an area of 50,000 square miles. The region of impact experienced severe soil liquefaction, leading to destruction of all nearby buildings, structures and roads. Huge elevation changes occurred near the region of impact. Vertical displacement also occurred around the region of impact. An area in Kodiak was permanently raised over 30 feet, while an area near Gridwood and Portage dropped 8 feet. Huge tsunamis were created, causing damages as far away as Hawaii and Japan. Towns that received major impact form the earthquake include Anchorage, Chitina, Glennallen, Homer, Hope, Kasilof, Kenai, Kodiak, Moose Pass, Portage, Seldovia, Seward, Sterling, Valdez, Wasilla, and Whittier.

Earthquake Overview

The Alaskan earthquake began when a fault between the Pacific and North American plates ruptured, caused by an oceanic plate sinking under a continental plate. The focus occurred at a depth of approximately 15.5 miles down. Before the quake, the Pacific plate moves toward the northwest at an estimate of 2 to 3 inches per year, compressing the crust of southern Alaska. This compression forced one region to be uplifted and the other region to be depressed. After thousands of years under compression, the stress was relieved by a sudden southeastward movement of the southern coastal region of Alaska, causing the great earthquake.

The epicenter of the earthquake was at Prince William Sound, 61.05°N 147.48°W, 80 miles east-southeast of Anchorage, and 40 miles west of Valdez (Hansen, 1966, pg 1). Figure 1 shows the location of the epicenter. This area is along the Alaska-Aleutian arc, marked as one of the world's most active tectonic regions in the world (Ruppert, 2007, pg 129). The arc stretches over 2000 miles from the Gulf of Alaska westward to Kamchatka. This arc also meets the Kamchatka-Kurile arc, which makes the combined length of over 3,500 miles. The Kamchatka-Kurile arc happens to have a much higher seismic activity because the plate is older and thicker prior to entering the subduction zone (Ruppert, 2007, pg 141). Being right along the Alaska-Aleutian arc, the chances of having earthquakes were not uncommon at Prince William Sound. In fact, over 60 earthquakes were recorded with a magnitude of over 7 before 1964 (Hansen, 1966, pg 7).

AftershocksThe long series of aftershocks after the earthquake also occurred on the fault between the Pacific and North American Plates, and gradually diminished in intensity over time. Within the first 24 hours of the initial quake, 28 large aftershocks followed, 10 of which were over 6.0 in magnitude. Thousands of these miniature quakes continued for over three weeks, near the region of impact. Twenty of these aftershocks were over a magnitude of 6.0. Within the first 69 days, 12,000 aftershocks were recorded with magnitudes over 3.5 (Hansen, 1966, pg 5). It took over a year for the aftershocks to finally settle to an unnoticeable level.

Water Waves - TsunamisMajority of the damage to properties and the loss of lives were due to water waves, caused by the initial shock of the earthquake, which inundated coastal communities (McCulloch, 1966, pg A1). Tsunamis, generated by large motion on the sea floor, devastated many towns along the Gulf of Alaska. It also caused serious damage to Alberni and Port Alberni, Canada, Hawaii, and the West Coast of the United States. The 1964 Alaska tsunami created by the earthquake was the second largest ever recorded. Waves were recorded to be over 200 feet in height. The shock also triggered many local waves, waves generated by underwater landslides in a local region. These local waves also caused heavy damage to nearby properties, such as boats, ships, bridges, and houses along the water coast.

Damages Caused to Affected Areas

Over 50,000 square miles were significantly damaged by the earthquake. It triggered many landslides, avalanches, tsunamis, and earthquake-caused fires. Towns that experienced major impacts form the earthquake include Anchorage, Chitina, Glennallen, Homer, Hope, Kasilof, Kenai, Kodiak, Moose Pass, Portage, Seldovia, Seward, Sterling, Valdez, Wasilla, and Whittier. There were major structural damages in cities all over Alaska. The damages totaled over $311 million (Hansen, 1966, pg 18). This is around $1.82 billion in 2012 currency value (Areppim, 2012). Because it was a low population area at that time, the death toll was relatively small for a quake with that magnitude. It was surprising how few people died in the city of Anchorage given the power of the tremor (Anchorage Museum, 1973, pg 2).

AnchorageAnchorage is located 75 miles northwest of the epicenter and it was the city that sustained the most severe property damage. Over 30 blocks of downtown Anchorage area had been damaged or destroyed. Most houses, buildings, and infrastructure were inadequately engineered and therefore did not survive the quake. This includes residential and commercial buildings, other structures, roads and vehicles. Even multistory buildings that were supposedly designed for earthquakes were also damaged heavily. Landslides in Anchorage were one of the main problems. They occurred at the business section of downtown Anchorage, at Government Hill, and at Turnagain Heights. Turnagian Heights experienced the largest and most devastating landslide after the Alaskan earthquake, as shown in Figures 2 and 3. It occurred in an area of about 130 acres and the land broke into many pieces and collapsed underneath, carrying all buildings down with it (Hansen, 1965, pg A59). Overall, 75 of these residential homes were destroyed. All utilities stopped working in Turnagian Heights.

WhittierWhittier, Alaska suffered the loss of 13 lives and $5 million worth of damages. At the time, Whittier only had 70 people (Kachadoorian, 1965, pg B1). Whittier is operated by the U.S. Government, primarily by The Alaska Railroad of the Department of the Interior and by the U.S. Army of the Department of Defense. Majority of the damages done to the town were caused by high tides and seismic shocks. When the initial quake stopped, all of Whittier’s port facilities were inoperable. Most facilities built on the slate and bedrock were either undamaged or slightly damaged by seismic shaking. Most of these buildings were concrete and wood framed structures. However, the buildings on unconsolidated sediments or fill were heavily damaged by seismic activity (Kachadoorian, 1965, pg B20). Majority of these buildings were also mostly concrete and other various types of construction. Regardless of the building materials, the site that the buildings were on was a more important factor.

Damages Caused to the Alaska's Transportation System

Figure 4: The rails were torn from their ties and buckled laterally. (Photo Credit: M. G. Bonilla, and U.S. Geological Survey)

Alaska Railroad SystemAlaska’s transportation systems were also severely damaged. The Alaska Railroad had damages totaling over $27 million. Most of this damage was between the terminals at Seward and Anchorage. Two railroad docks, valued at $4 million were completely destroyed, along with 50 freight cars (Hansen, 1966, pg 25). Damage to these railroads were caused by direct seismic shaking, landslides, subsidence, ground cracks and lurching, and inundation by high tides. Seventeen railroad bridges were badly damaged or destroyed. Figure 4 shows a common failure case for railroad tracks; the vibration caused the rails to buckle laterally.

Alaska Highway SystemThe Alaska Highway system also experienced damages which were mostly the destruction of bridges, cracking of roads, and differential subsidence of fills. The highway system repairs cost over $21 million. Because of this earthquake, an upgrade to a higher standard was needed and that put the cost over $55 million (Hansen, 1966, pg 27). The Seward Highway between the Ingram Creek and Potter section was severely damaged along with its 22 bridges. Large pavement cracks caused by differential subsidence of fills, can be seen everywhere. Figure 5 shows the fissures in the highway along Turnagian Arm. Regardless of how well the seismic design for the road is, it can never provide complete safety in a fault zone where ground rupture will occur (Kubba, 2008, pg 301). The Richardson Highway managed to survive with minimal damages but there were visible pavement breaks. The partially completed highway, Copper River Highway, also suffered severe damage. Almost every bridge along this highway was destroyed, including the famous Million Dollar Bridge, as shown in Figure 6 and 7. One span of the Million Dollar truss bridge fell into the Copper River below. Around Kodiak, the highways were mostly destroyed by sea waves along with tectonic subsidence.

Streets and RoadsMany streets and roads experienced soil liquefaction, cracks, collapse, or vertical displacements. Figure 8 shows the collapse of Forth Avenue in downtown Anchorage, due to ground failure on the site. This was not an uncommon site as it happened to many places.

Airports Airports were also damaged, but not as much compared to other transportation systems. The total lost was estimated to be around $3.3 million (Hansen, 1966, pg 29). The Anchorage International Airport suffered the greatest damage. One person died in a collapsing control tower under the seismic vibration. 20,000 barrels of aviation fuel were lost from damaged storage tanks. The control tower at Elmendorf Air Force Base, close to the Anchorage International Airport, suffered from cracks over 15 feet long, beginning from its base. For the other airports, Cordova, Homer, Kodiak Naval Station, Seldovia, Seward, and Valdex, damages were overall light.

Figure 9: The Hillside Apartments Building, left, and the three-story wood frame building, right, was compared. Wood-frame buildings performed better against the earthquake in Anchorage. (Photo Credit: U.S. Geological Survey)

Building Performances

Early photographs showed severe property damages in cities all over Alaska. A majority of large buildings were damaged from the acceleration forces on the buildings and lack of frame action. Foundation failures were the primary cause of collapse that occurred to small buildings and houses. Also, buildings with different structural materials performed differently under the earthquake. For example, the Hillside Apartments was a steel framed construction and was damaged beyond repair after the quake. However, the building next to it was wood frame construction and it survived with minor damages, shown in Figure 9. In total, over 215 homes were destroyed and 157 commercial buildings were vacated in the city of Anchorage alone.

Figure 10: The Hillside Apartment Building in Anchorage was torn down after being severely damaged by the earthquake. (Photo Credit: U.S. Geological Survey)

Hillside ApartmentsThe Hillside Apartments were severely damaged and could not be repaired, shown in Figure 10. They were located between G and H streets on 16th Avenue. The building had a split-level design, five stories high on one side, and three stories high on the street side. The structural materials were post-and-lintel frame with steel-pipe columns, rolled-steel beams and concrete floor slabs on steel joists. All walls were unreinforced hollow concrete blocks. The building failed due to lack of resistance to shear (Hansen, 1965, pg A25). Shear occurred in an east-west direction at the third floor on the south side and at the lower stories on the north side. The roof of the building displaced a little to the west. No code provision had been made during this time for resistance to strong lateral seismic stress (Hansen, 1965, pg A26).

Wood Frame buildingsWood framed buildings performed relatively well with little to no damages compared to other construction types. Wood frame walls that were properly constructed behave in an amazingly rigid unit that had the capacity to resist the shock and impact forces from the quake. On the houses examined, plywood did an amazing job. For most of these buildings, the plywood was applied with the 4 by 8 foot sheets placed vertically, with perimeter nailing, and that was enough to give the walls its rigidity (U.S. Department of Agriculture, 1964, pg 6). The majority of the wood framed buildings have a type of basement or crawlspace. Even when these foundations were destroyed, the houses were still partially supported on solid ground.

Wood frame floor systems also performed relatively well with little to no damages. The wood floor and the wall systems were strong and were able to support the weight of the house even if when the foundations had failed (U.S. Department of Agriculture, 1964, pg 5). But some failures happened when the floor had pulled itself away from the wall. If diagonal wood or plywood sheathing were nailed to both the floor and the wall, this failure could have been easily prevented. As for a majority of wood frame roofs, they did not collapse even when the foundation walls had been destroyed.

J.C. Penney’s Department StoreJ.C. Penney’s Department Store was a new building that partially collapsed under the earthquake and had to be torn down, shown in Figure 11 and 12. The building was a reinforced concrete-structure, five-story high, having shear walls on three sides and a curtain wall made of precast panels on the north. The floor slabs sheared at the connections to the column wall on the east side of the building (Hansen, 1965, pg A26). This caused the collapse of the northeast corner of the building and scattered precast panels all over the street below. The building also failed under torsion, caused by rotational displacements from an eccentric load. This rotation sheared off the support of the west wall at the second level at the north end. As a result, all floors and walls above collapsed right on top of it.

Alaska Psychiatric InstituteAlaska Psychiatric Institute building was a steel-framed, three-story building that surprisingly sustained little damage. Part of the reason was that the building was located southeast of downtown Anchorage, where the site suffered minor soil liquefaction. Minor cracks were seen in stairwells and pieces of acoustic ceiling tiles dropped to the floor (Hansen, 1965, pg A23). Broken pipes were reported on the third floor and were quickly repaired (Rogers, 1964, pg 243). Some floor tiles buckled at the joints. Overall, this building had very little damage compared to the rest of the buildings in Anchorage. In addition, the neighboring buildings, Providence Hospital and Alaska Methodist University, also had very little damage. The main reason for this was because the three buildings were on a site that did not suffer from soil liquefaction.

Figure 13: Travel times for the tsunamis, in hours, produced by the 1964 Alaska earthquake, in red, and by the 1960 Chile earthquake, in purple. (Photo Credit: U.S. Geological Survey)

1960 Chilean Earthquake Comparison

The Alaskan earthquake was the second largest earthquake ever recorded, right after the largest, the 1960 Chilean earthquake. The 1960 Chilean earthquake was also a megathrust earthquake, caused by the release of stress between the subducting Nazca Plate and the South American Plate, on the Peru-Chile Trench. According to USGS, the May 22nd, 1960 Chilean earthquake was a 9.5 magnitude earthquake that caused over 1600 deaths, 3000 injured and over $550 million in damages. It even caused over $500,000 damage to the west coast of the United States. Over 2 million people were left homeless when their homes were destroyed. Like most large earthquakes, other natural disasters were triggered. This earthquake created tsunamis that caused damage to southern Chile, Hawaii, Japan, the Philippines, eastern New Zealand, southeast Australia, east coast of the United States, and Alaska. Figure 13 below compares the 1964 Alaskan earthquake, and the 1960 Chile earthquake tsunami waves’ travel times, in hours. Local tsunamis severely battered the Chilean coast with extremely high waves. Other natural disasters that occurred after the initial quake were numerous landslides, floods and the eruption of Cordon Cauelle. Overall, compared to the 1960 Chilean earthquake, the 1964 Alaskan earthquake had a lot less loss of lives, but the costs of damages were roughly around the same.

1957 Andreanof Island Earthquake

The 1957 Alaska earthquake, more commonly known as the 1957 Andreanof Islands earthquake, took place on March 9, 1957. It was also a megathrust earthquake that happened along the Alaska-Aleutian arc. This earthquake had a magnitude of 8.6 and was centered at the south of the Andreanof Islands. Adak Island, Umnak Island, and Hawaii were the main places that suffered damages, but no lives were lost from the quake.

Lessons Learned

Before 1964, not much research on the origins and mechanisms of earthquakes, on crustal structure and makeup, and on generation and prediction of tsunamis had been done (Eckel, 1970, pg 37). The Alaskan earthquake provided many opportunities for scientists and engineers to research these topics. They are now using every large scale earthquake as a full-scale laboratory study to gather scientific and engineering information.

When studying the Alaskan earthquake, one of the most valuable lessons learned was the value of pre-earthquake information. This information will help before and after an earthquake. Base maps, topographic maps, hydrographic charts, pertinent reports and maps on local geology and soils, were created or improved after the earthquake (Eckel, 1970, pg 42). These will be provided as tools for scientists and engineers to develop effective ways for earthquake forecasting as well as damage controls. Detailed city plans and map of the utility systems were required and will help the relief and rehabilitation of the general public in future emergencies. The official seismic risk map at that time was lacking in detail. Better earthquake-hazard maps, based on improved knowledge from the earthquake were made following the 1964 quake.

As for buildings, many new buildings after the earthquake were designed to withstand intense shaking, while the older buildings have been reinforced (Haeussler, 2003, pg 1). New developments in known hazardous areas are strongly discouraged. Ports, docks, and canneries cannot be built on steep-faced deltas or other deposits of unconsolidated materials that are marginally stable under seismic conditions, in order to minimize damages. But despite all efforts, earthquakes will still cause damage in the future. Therefore, people always have to be prepared for the next earthquake to minimize damage. The consequences of having a large earthquake now could be much greater than the earthquake in 1964 (Wesson, 1999, pg 3).

Preparing for the next big earthquake Even now, Alaska is still educating people to be prepared for earthquakes. That is because Alaska is one of the most seismically active areas of the world (Haeussler, 2003, pg 1). Four major areas of concern that people need to learn are, what to do during and after an earthquake, how to prepare for an earthquake, assessing your risk from earthquakes, and preparing for tsunamis (Haeussler, 2003, cover pg). Helping people understand the answers to these questions will help save a lot more lives if and when the next big earthquake occurs. Simple guides, such as “take cover under a study desk” or “Don’t Run Outside” are enough and are easy to remember. With the combined effort of AEIC, UAF, USGS, FEMA, DHS&EM, ADGGS, ConocoPhillips, and WC/ATWC, a pamphlet was created with all the information needed to be prepared and are available to everyone.

Report: investigates all the damages that the earthquake caused at Whittier, Alaska. The problems were similar to what happened in Anchorage, which range from landslides, collapsing buildings, loss of lives, and much more.

Review: explains the Alaska-Aleutian and Kamchtka-Kurile arc in detail on why they are one of the most active tectonic margins in the world. Many examples of the 1964 Alaskan Earthquake were given and also were compared to other earthquakes.

Pamphlet: informs readers how to be prepared for the next big earthquake that may be hitting Alaska. Information here was written from the lessons learned from the 1964 earthquake. All information is backed up by many different earthquake engineering societies.

Book: provides general design considerations for seismic consideration. A picture of the Alaskan earthquake is shown and stating that complete safety can never be provided when ground rupture is occurs.

Website Tool: converts the input dollar amount from a year in the past to the desire target dollar amount for a target year.

AnchorageAnchorage is located 75 miles northwest of the epicenter and it was the city that sustained the most severe property damage. Over 30 blocks of downtown Anchorage area had been damaged or destroyed. This includes residential and commercial buildings, other structures, roads and vehicles. Many multistory buildings were damaged heavily. Landslide in Anchorage is one of the main problems. It occurred at the business section of downtown Anchorage, at Government Hill, and at Turnagain Heights. Turnagian Heights experienced the largest and most devastating landslide after the Alaskan earthquake. It occurred in an area of about 130 acres and the land broke into many pieces and collapsed underneath, carrying all buildings down with it. 75 of these residential homes were destroyed. All utilities had stopped working in Turnagian Heights.